Visual screening for licensure may need to be updated to reflect current research, which shows that visual acuity may not be the best indicator of safe driving ability. Photo: Photo by Wonderlane on Unsplash.

It’s required by law that all drivers in the United States undergo vision screening prior to obtaining their license. However, researchers of a recent study argue that using this measurement of visual function to determine whether an individual is allowed to drive may cause more harm than good, especially for the senior population. The study found that while the number of motor vehicle collisions experienced by those with impaired visual acuity exceeded that of the general population, the effect was not significant enough to outweigh the negative impacts of involuntary driving cessation, including those on mental health and mobility.

The population-based sample consisted of 2,000 licensed drivers 70 and older residing in Alabama. During the baseline visit, the following measurements were performed on all participants: visual acuity, contrast and visual field sensitivity, the Useful Field of View test and the Motor-Free Visual Perception test. The cohort was then followed for up to four years for involvement in police-reported motor vehicle collisions. After the study period, the researchers determined the screening performance of each visual function in regard to motor vehicle collision occurrence by calculating values for area under the curve (AUC), sensitivity and specificity; in addition, they estimated rate ratios for the association between each visual function measure and motor vehicle collision.

Throughout the four-year follow-up period, 359 motor vehicle collisions occurred, and 16% of the cohort was involved in at least one collision. The researchers found that “less than 10% of the study participants had impaired visual acuity or contrast sensitivity, as defined by clinical cutpoints, and the prevalence of Useful Field of View impairment was slightly greater than 10%.” They also determined that none of the measurements of visual function exhibited adequate values for sensitivity or specificity, and AUC values were only about 0.5.

“For all visual function measures except visual acuity, there were statistically significant positive rate ratios for the association between vision impairment and future motor vehicle collision occurrence, though the magnitude of the associations were weak,” the researchers noted. “When considering all of the measures collectively as a test battery, the results similarly demonstrated inadequate sensitivity and specificity for being a general population screener.”

The researchers concluded, “The results of the current study indicate that such screening will unduly penalize older drivers who, while at increased risk for motor vehicle collision, are not likely to experience one.” They suggest alternative approaches to improving driver safety, particularly for seniors, include driver evaluation and training programs, transportation alternatives and targeted screening initiatives.

McGwin Jr. G, Owsley C. Vision screening for motor vehicle collision involvement among older drivers. Ophthalmology. April 18, 2022. [Epub ahead of print].